Fuel injection system for internalcombustion engines



Feb.'20,1940. A 2,191,186-

FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES File d Dec. 28, 1936 2 Sheets-Sheet 1 A liar yfs G. AMERY FebVZO, 1940.

FUEL INJECTION SYSTEM FOR INTERNALCOMBUSTION ENGINES Filed Dec. 28, 1936 2 Sheets-Sheet 2 it' l IIIO G'I Patented Feb. 20, 1940 UNITED STATES PATENT OFFICE George Amery, London, England Application December 28, 1936, Serial No. 117,964 In Great Britain December 31, 1935 6 Claims.

This invention comprises improvements in or relating to fuel injection systems for internalcombustion engines.

The invention relates to internal-combustion engines of the compression ignition type. I have found that in such engines it is desirable that the pressure of injection of fuel should be a function of the speed of the engine. The employment of a higher injection pressure tends to reduce the delay period which exists between the commencement of the admission of fuel and the commencement of itsignition. At higher engine speeds the time available for ignition is reduced. Consequently the reduced delay period resulting from a higher injection pressure suits the conditions of high engine speed. i

In United States Patent No. 2,053,312 there is described an injection system in which there is provided a relief valve the setting of which determines the maximum injection pressure.

According to the present invention in a fuel injection system in which a relief valve is provided for limiting the maximum injection pressure means are provided for modifying the pressure at which the relief valve will operate in accordance with the engine speed.

The means for modifying the relief valve pressure may comprise a centrifugal governor oper atively connected to a member for resisting the opening of the relief valve. There may further be provided in combination with the above means for delivering fuel under injection pressure to the injection devices such that the fuel delivery in a given time is proportional to engine speed. The relief valve and means for delivering fuel at injection pressure may be each connected to a fuel delivery conduit which is common to a plurality of injection devices, separate means being provided to deter- 40 mine the order and time at which the injection devices operate for the injection of fuel.

In one form the fuel injection devices are of a type in which the-admission and termination of fuel injection is determined by the application or removal of fluid pressure to a controlling piston.

Preferably the controlling piston is a closing piston, the application of fluid pressure to which shuts the valve and the means to determine the order and time at which the injection devices 50 operate comprises a distributor which distributes fluid under pressure to the closing pistons from a branch connection of the fuel delivery conduit so that the closing pressure is proportiom al to the fuel injection pressure.

The relief valve may comprise a valve member,

a spring to resist the opening of the valve member, centrifugal governor weights and means for rotating the same and operative connections between the governor weights and the spring to sustain the spring against the pressure of the valve member under the influence of the centrifugal force exerted upon the governor weights.

The following is a description by way of example of one form of fuel injection system in accordance with the invention:

Referring to the accompanying drawings Figure l is a diagram of the connections of the system as a whole;

Figure 2 is a longitudinal central section through a relief valve in accordance with the invention, and

Figure 3 is a cross-section upon the line 3-3 of Figure 2.

Referring to the drawings in Figure 1 ill rep resents a fuel pump for delivering fuel under pressure from a fuel tank it to a pipe line it at injection pressure. The pipe line it is provided with branches i l to fuel injectors it allocated one to each cylinder of the engine. The branches Ml enter chambers it in the fuel injectors where the fuel, under the injection pressure surrounds a needle valve ll bearing on a seating it. The needle valve has a shoulder it which is subject to the fuel pressure and the pressure tends to lift the valve ll off its seating. The pump it is such as to maintain ,a uniform continuous pressure in the fuel supply pipe it and around the injector needle valves ll. Each injector has, moreover, an enlarged head which constitutes a closing piston Zll to which fluid under pressure is admitted through a distribution pipe such as 2i and in addition there is a spring 22 which assists to keep the needle valve ll closed.

It will be understood that each of the fuel injector nozzles it is secured in the combustion chamber of an engine cylinder in an appropriate position, as is well known. Drain pipes 23 serve to carry away any fluid which leaks past the pistons ill or 26.

Connected to the pipe line it there is a relief valve it which determines the injection pressure and the pump l l is made of sufficient capacity to ensure that even at full load fuel will be able to escape through the relief valve 2t. Drainage from the relief valve E i and from the drainage pipes 23 can, if desired, be led back to the fuel tank l2, as indicated by pipe 5d. The construction of the relief valve M is hereinafter detailed.

In order to determine the distribution of fuel under pressure to the closing pistons 26 of the fuel injection nozzles a distributor 25 is provided. In the connections as drawn in Figure 1 the distributor 25 is supplied with fuel under pressure by a branch26 from the fuel conduit l3 but the distributor might be provided with an alternative source of fluid under pressure if desired so long as an adequate quantity and pressure of fluid are provided to operate the pistons 26. It will be observed that the closing pistons 20 are of larger area than the shoulders l9 which constitute the opening pistons for the needle valve l1 and therefore even a lower pressure than the injection pressure applied in the chamber I6 may 'suflice to keep the needle valve I! of each fuel nozzle shut. If, however, pressure is released from behind the closing piston 26 the needle valve will immediately open due to the pressure of the injection fuel in the chamber l6. Four separate fluid distribution conduits 2|, 3|, 4|, 5| are provided for the four injector nozzles l5 and each of these is led to a separate distribution valve casing 32, 33, 34, 35 on the distribution unit 25. The details of the distribution unit 25 in themselves form no part of the present invention.v

It is sufiicient here to state that each of the valve casings 32, 33, 34, 35 contains a piston valve operated by a cam within the unit 25 for determining the admission ofifuel under pressure to the closing pistons 26 and preferably this cam is provided with means for advancing and retarding the time of the operation and also for modifying the period during whlchthe pressure is applied to the pistons 20. v I

Referring to Figures 2 and 3, which show the relief valve 24 'in detail, the valve comprises a hollow casing having a projecting bearing 55 at one end through which passes an operating shaft 56 driven at aspeed which'is proportional to the engine speed, for example from the usual valveoperating cam shaft of the engine. The pump ll may be operated by the same shaft, as indicated in Figure 1.

' weight 64.

The shaft 56 is supported in ball bearings 51, 58 and has an enlarged head 59 within the casing 24 which is slotted diametrically as indicated at 60. Two pivot pins 6|, 62 cross the slot 66 and each supports a governor lever 63 bearing a The two levers are similar to one another and are disposed at opposite sides of the axis so as to be in balance with one another. The

levers each have an abutment 65 which supports a ball race 66 taking the reaction of a valve spring 61. The valve spring 61 is co a xial with the'shaft 56 and bears on a carrier/66 rotatably received in the end of head 56; in the opposite end of which there is slidably/moulnted the stem of a relief valve 69. The relief valve has a head 16 within the carrier on ,which bears a spring I'll so that the relief valve is pressed as far as possible out of the carrier, towards: the right as shown in Figure 2.

The relief valve 69 bears on a seating II in a valve block 12 which fits into and closes the end of the casing 24 of the relief valve. The valve block.12 is adjustably retained in place by a screwed ring I3 and it is centrally boredwith the passage 14 connecting the seating II with the pipe 15 which is a branch of the fuel supply conduit l3. Consequently fuel under pressure bears upon the end of the relief valve 69 but the opening of the relief valve is resisted by the spring 61, the reaction of which is taken by the governor levers 63.

The carrier 66 has a projection I6 the end of which is spaced somewhat from the adjacent thrust plate of the ball bearing 66. In this way when the valve 69 is opened a. vcertain distance the lost motion between the projection 16 and the thrust race 66 will have been taken up and further movement of the valve 69 will be resisted, not by the spring 61 but by the spring I'll which is a stiffer spring than the spring 61.

The valve 69 has a head 11 which is surrounded by an enlarged portion 18 of the bore in which the valve works and beyond the enlarged portion 18 there is a short section of bore 19 which is of such a size as to closely fit the head 11. Beyond the section 19 is a second enlargement 60 which is connected by a channel 8! to the drain pipe 54. Moreover, the conduit 14 which is connected to the branch 15 and conveys fuel pressure to the end of the valve 69 receives an extension 82 on the end of thevalve 69.

The governor levers 63 are also provided with abutments 83 which bear against-stop pins 84. The stop pins 84 are slightly eccentric on their shanks 85 which find a bearing in the head 59 of the shaft 56. By rotating the stop pins the stops 63 can be adjusted so that the governor levers are pressed against the stop pins evenly by the spring 61 when the driving shaft 56 is not revolv- The pump I! which delivers the fuel under pressure to the conduit I3 is of such a type as to deliver fuel at a rate proportional to engine speed. w I I The operation of these parts is as follows:- The pump l l delivers fuel under. pressure to the conduit I3 and owing to the operation of the distributor 25 pressure is relieved from the back of each of the pistons 20 of the various fuel injection nozzles in turn. This allows fuel under r the relief valve 24.

At starting it is necessary to have a high injection pressure for the first few revolutions until 7' the engine gets under way. This is accomplished by the extension 82 of .the relief valve 69, which being of smaller area than the head 11 ensures that the valve will only open under a pressure 'in excess of that allowed by the head 11. As

soon as the valve 69 has been lifted off its seat suificiently for the extension 82 to clear the passage 14 the fuel pressure acts on the full area of the head 11, which is soproportioned that at this time the head has entered the portion of the bore 19 which fits it. Consequently the fuel pressure, acting on this larger area forces the valve 69 further to the left compressing the spring 61 until almost the whole of the.lost motion between the extension 16 and the thrust plate 66 has been so taken up. In this position the head ll just passes the constricted portion I9 and reaches the enlargement 86 of the bore in which the relief valve works. Further movement of the relief valve 69 will open an annular area between the edge of 65 the constricted portion 19 and the edged the head H of the valve thus permitting fuel to escape to the drain channel 8|. In this position of the relief valve it maintains a predetermined minimum pressure of injection (1. e., the injection pressure required at idling speeds) and in this position the end of the projection 16 is not in actual contact with the adjacent thrust plate of the bearing 66 although close to it, and the centrifugal force tending to open the governor weights is I, portional to the square of the engine speed because the force on the governor weight 64 will be proportional to the square of the engine speed. Consequently the injection pressure will be sufficient at the increased speed to maintain the same 2 fuel delivery through the valve ll notwithstanding the shorter time during which the valve is opened. For a given setting of the distributor therefore the engine will continue to receive the same amount of fuel as before. The regulation of the admission of fuel in accordance with the load is accomplished by the distributor 25 as above described. At engine speeds leading to a fuel pressure in excess of the strength of spring I'll, this spring will yield and thus prevent overstraining of the pipework and other parts by excessive fuel pressure.

I claim:

1. In a fuel injection system the combination of a pressure conduit, a relief valve for limiting the maximum injection pressure in said conduit, means for modifying the pressure at which the relief valve will operate in accordance with the engine speed, said means comprising a centrifugal governor operatively connected by resilient means to the relief valve, said relief valve comprising a valve member having a stem extension of smaller diameter than its normal head and fitting into said presure conduit whereby an increase of injection pressure is provided at the commencement of operation.

2. In a fuel injection system for an internalcombustion engine the combination with a fuelpump and means to distribute fuel therefrom to the engine, of a relief-valve casing having a bore connected to the fuel distribution means, a

valve-plunger in said bore capable of uncovering a relief-opening after a predetermined movement, a spring opposing the movement of the valveplunger, 2. reaction-member on which the spring bears, a stop mounted to move with the valve plunger in line with a face associated with the reaction member so as to limit the movement of the valve-plunger against the spring and so lo cated as to come into engagement with said face approximately simultaneously with the uncovering of the relief-opening and a centrifugal governor having centrifugally actuated elements which are operatively connected to the reaction member to sustain the same.

3. A fuel injection system as claimed in claim 2, wherein the said spring bears on the head of a carrier for the valve-plunger and an overload spring is interposed between the carrier and the valve-plunger.

4. A fuel iniection system as claimed in claim 2, wherein the valve-plunger has an extension capable of entering an extension of the bore in the relief-valve casing of smaller diameter than the main part of the bore, so as to give an extra high injection pressure at starting.

5. In a fuel-injection system the combination of fuel-injection devices, fuel pressure supply means, a supply system connecting the supply means to the injection devices, a relief=valve for closing a port in said supply system, a relief-valve carrier-member, a centrifugal governor, resilient means interposed between the carrier member and the centrifugal governor and a stop on the carrier for limiting the extent of yield of said resilient means, said governor being the reactionproviding element against the opening of the relief valve after the engagement of the stop.

6. In a, fuel-injection system as claimed in claim 5 the provision of a second resilient means interposed in series between the carrier member and the valve, said second resilient means being substantially stronger than the one between the carrier member and the governor.

GEORGE .1 in, a Y 

